Damsel gasping

[Chunk87]

Hi all. I hope this is in the right place.
I've had my 50g with 20g sump set up running for about 12 weeks and have started adding fish. I've got a pair of clowns, a randalls goby, and a pair of yellow tail blue damsels.
All the fish have been fine and feeding, but today one of the damsels is really gasping and just sitting at the bottom of the tank. None of the other fish are gasping at all and are swimming and feeding fine.
I tested my tank two days ago and it was:
Ammonia: 0
Nitrate: 0
Nitrite: 2

Does anyone have any suggestions to help save the little guy?

I'll do another water test when I get back home from work.

 

[Newsmyrna80]

How long have you had the damsels? Did you quarantine them?

 

[ai4ns]

I had this issue with somes clown before actually - was swimming fine and then after few days they would just start gasping at the bottom of the tank. I did a lot of research on this topic with all signs pointing to the fish being sick and with all the moving between tanks + dramatic water changes just too much for its little body.

You can try taking him out of the tank and put him in a smaller one (no lights) and see how that goes but I don't think the lil guy will make it. Defiantly quarantine them if you don't.